Halide Perovskite Research Articles

A Redox-Active Ionic Liquid Surface Treatment for Healing CsPbBr3 Nanocrystals.

Additive engineering of lead halide perovskites has been a successful strategy for reducing a variety of deleterious defect types. Ionic liquids (ILs) are a unique group of such additives that have been used to passivate halide vacancies in both bulk lead halide perovskites and their colloidal nanocrystal analogues. Herein, we expand the types of defects that can be addressed through IL treatments in CsPbBr3 nanocrystals with a novel phosphonium tribromide IL that heals metallic lead surface defects through redox chemistry. This new type of surface treatment leads to a significant increase in PLQY and outperforms equivalent treatments with non-redox-active bromide ILs. Such redox-active ligands widen the scope of defect types that can be addressed in semiconductor nanocrystals.

Förster Resonance Energy Transfer in Metal Halide Perovskite: Current Status and Future Prospects.

Förster Resonance Energy Transfer (FRET) is a non-radiative energy transfer process in a donor-acceptor system and has applications in various fields, such as single-molecule investigations, biosensor creation, and deoxyribonucleic acid (DNA) mechanics research. The investigation of FRET processes in metal halide perovskites has also attracted great attention from the community. The review aims to provide an up-to-date study of FRET in the context of perovskite systems. First, we discuss the fundamentals of FRET process, and then summarize the recent progress of FRET phenomenon in perovskite-perovskite, perovskite-inorganic fluorophores, perovskite-organic fluorophores, and organic fluorophores-perovskite systems. Finally, we speculate on the future prospects of roles of FRET in the implications for the overall performance of optoelectronic devices based on these systems, as well as the challenges in maximizing FRET efficiency.

Exotic ferroelectricity in strained BaZrS3 chalcogenide perovskite for photovoltaics

Ferroelectricity in solar cells is credited with a multitude of benefits, including improved charge carrier separation and higher than band gap device voltages, however most ferroelectrics are wide-gap materials that generate very little photocurrent. Some halide perovskites are ferroelectric, but they suffer from degradation, despite their otherwise excellent performance. Recently, BaZrS3, a chalcogenide perovskite has received attention due to its optimal band gap, non-toxicity, and superior stability. The ground state of BaZrS3 is reportedly a GdFeO3-type distorted perovskite (space group Pnma). Here, using first-principle calculations, we show that the polar Pna21 is thermodynamically as stable as Pnma. This new phase is weakly ferroelectric, exhibiting a net polarization of 0.27 µC/cm2 and a d33 piezoelectric coefficient of only ~1 pm/V. Under strain, the interplay between out-of-plane and in-plane octahedral tilts amplifies spontaneous polarization, spin splitting, and large polaron radii. These exotic traits are comparable to those of the popular halide perovskites.

Large Scale Lead-Free Perovskite Polycrystalline Wafer Achieved by Hot-Pressed Strategy for High-Performance X-Ray Detection.

Halide perovskites (HPs) have demonstrated excellent direct X-ray detection performance. Lead-free perovskite polycrystalline wafers have outstanding advantages in large-area X-ray imaging applications due to their area-scalability, thickness-controllability, large bulk resistivity, and ease of integration with large-area thin film transistor arrays. However, currently lead-free perovskite polycrystalline wafers possess low sensitivity, typically less than 1000 µC Gy-1 cm-2, which severely limits their X-ray detection applications. Here, high-quality and large scale polycrystalline wafers of AG3Bi2I9 (AG: aminoguanidinium) with short intercluster distances are successfully prepared using a hot-pressing method. The wafers possess high mobility-lifetime product of 5.66 × 10-3 cm2 V-1 and therefore achieve high X-ray sensitivity of 2675 µC Gy-1 cm-2, which can be comparable to those of the high-quality single crystal counterpart reported by the previous research (7.94 × 10-3 cm2 V-1 and 5791 µC Gy-1 cm-2), and represent the best results of the currently lead-free HP polycrystalline wafers. Besides, the wafers exhibit the X-ray detection limit as low as 11.8 nGy s-1, excellent long-term working stability, and high spatial resolution of 5.9 lp mm-1 in imaging. The findings demonstrate that AG3Bi2I9 polycrystalline wafers are feasible for high-performance X-ray detection and imaging system.

Mapping of Internal Ionic/Electronic Transient Dynamics in Current-Voltage Operation of Perovskite Solar Cells.

Metal halide perovskites are mixed ionic-electronic semiconductors that involve an important and particular phenomenology that negatively affects the performance and stability of next-generation photovoltaic devices based on such material. The ionic nature of perovskites is shown to undergo not only a simple redistribution of charges but also influences the electronic processes and ultimately the steady-state device operation. Nevertheless, a comprehensive understanding of the internal contributions of ionic and electronic conductivities to the evolution of current during device performance experiments and to degradation losses in ageing tests is currently missing. Here the ionic- and electronic-based currents are separately shown in photovoltaic perovskites by means of transient experiments, beyond the external measured response. From an advanced mathematical model, the experimental observations attributing the partial transient features to physical effects in perovskites are rationalized. It is revealed that ion-driven surface recombination effects are a dominant factor in the slowdown of efficiency measurements and in the long-term degradation of perovskites under operational conditions. This work contributes to tracing a more accurate physical picture of the complex energy landscape of the perovskite-based solar cells, which will be key to taking steps toward industrialization.

Ab-initio atomistic insights into lead-free perovskites for Photovoltaics Technology

The primary objective of this manuscript is to enhance knowledge and comprehension of hexagonal perovskites KNiX3 (X=I, Br). The world is fascinated by halide perovskites because of their advancements in opto-electronic applications, particularly in the photovoltaic field. KNiI3 and KNiBr3 halide perovskites correspond to the two anion I and Br. Here we aim to investigate how opto-electronic applications are affected by the substitution of cations and anion. Within the framework of density functional theory (DFT), the structural, electronic, and optical properties have been computed using the PBE GGA approximation. Br-based perovskites have a shorter bond length than I-based compounds because iodine ions have a larger ionic radius than bromine ions. Thus, the lattice constant increases from I-based potassium halide perovskites to Br-based potassium halide perovskites. The values of the lattice constant match the results of experimental computations. The Density of States (DOS) curves and band structure are used to examine the contribution of the bands. From Br to I, there is a reduction in the band gap, indicating an improvement in photovoltaic applications. Various energy ranges are used to calculate the optical spectra, dielectric function, absorption coefficient, optical reflectivity, and refractive index. KNiX3 (X=I, Br) compound reveals low reflection value which is typically an excellent choice for photovoltaic and opto-electronic applications.

Nanomolar level detection of phosphodiesterase 5 inhibitor drug tadalafil based on halide perovskite@HNTs nanocomposite electrode

As halide perovskites have taken a central role in the evolution of semiconductor materials, they are setting new standards for performance and revolutionizing the energy sectors. Unfortunately, little light is shed on the material's electrochemical sensing capabilities. This work reports the synthesis and characterization of a novel double halide perovskite Cs2CaSnCl6 (HDP) integrated with halloysite nanotubes (HNTs) for the electrochemical detection of Tadalafil (TAD). HDP@HNTs nanocomposite is synthesized using a simple solvothermal method and is characterized using various techniques like SEM, TEM, UV-visible, FT-IR, TGA/DTA, XRD and BET analysis. The results obtained from these characterizations confirmed the successful formation of the nanocomposite, revealed the material's endurance to high temperatures and the availability of a large surface area for reaction. Electrochemical characterization techniques like cyclic voltammetry (CV) and linear sweep voltammetry (LSV) demonstrated a linear correlation with the concentrations of TAD. Computational analysis of the TAD structure optimization, molecular electrostatic potential (MEP) of TAD and calculations regarding the HOMO-LUMO molecular orbitals are all carried out using the DFT/B3LYP method. The HDP@HNTs sensor is capable of achieving the lowest detection limit of 1.68 nM and the limit of quantification of 5.09 nM. The material showcased a remarkable sensitivity of 0.0104 µA nM-1 cm-2 from all the electrochemical parameters. Its reliability and stable performance even in the presence of real samples makes it a promising material for sensing applications. Thus, the reported framework contributes to the advancement in the development of sensors and enhanced healthcare outcomes.

SnS2-supported MAPbI3 composites for effective photocatalytic hydrogen evolution

Metal halide perovskites have demonstrated encouraging photocatalytic potential due to their favorable photoelectric properties. However, severe carrier recombination greatly affects their catalytic performance. Here, we introduced cocatalyst SnS2 to synthesize novel SnS2/MAPbI3 composites via the electrostatic coupling method, which presented excellent hydrogen production performance. The hydrogen production rate of 5 % SnS2/MAPbI3 (5 wt% SnS2/MAPbI3) reached 445.96 μmol·g−1·h−1, about 325-fold increase compared to pure MAPbI3 (1.37 μmol·g−1·h−1). The 16 h cycle stability test proved its stability and effectiveness. Detailed experimental characterizations and analysis indicate that the cocatalyst SnS2 reduces the surface overpotential and facilitates electron transport and efficiently separates photogenerated charge carriers. This work provides new insights into effective photocatalysts based on MAPbI3.

Lead-Free Halide Double Perovskites for Sustainable Environmental Applications

The development of renewable energy sources has become a crucial objective in today's world due to increasing environmental concerns and the depletion of fossil fuels. Solar energy has emerged as a promising alternative. In recent years, there has been a significant focus on perovskite solar cells due to their remarkable power conversion efficiencies and their ability to be produced in a cost-effective manner. These cells have attracted considerable attention from researchers and industry professionals alike. However, traditional perovskite materials often contain toxic lead, raising concerns about their environmental impact and long-term sustainability. This article highlights the environmental concerns associated with lead-based perovskite materials and explores the advantages, challenges, and potential of lead-free halide double perovskites as sustainable alternatives for achieving an enlightening and sustainable future in the field of photovoltaics. Lead-free halide perovskites have been an area of active research in the field of nanotechnology and material science due to their potential for various applications. We provide an overview of perovskite solar cells as a promising technology, discussing their material properties and device performance. Furthermore, we present a comparative analysis between lead-based and lead-free perovskites, emphasizing the challenges and future perspectives associated with the development and implementation of lead-free alternatives. Through this analysis, we aim to shed light on the potential of lead-free halide double perovskites and inspire further research in the quest for environmentally friendly materials for solar energy applications.

Highly efficient tunable mid-infrared luminescence achieved by crystal field modulation of CsPb1-xHoxBr3 halide perovskite AlF3-based fluoride glass

Mid-infrared (MIR) light sources have gained significant importance across various applications in spectroscopy, sensing, astronomy, communications and medical surgery. The diverse spectral characteristics of rare earth ions, particularly lanthanide ions, stemming from their distinctive 4f intershell transitions, offer a multitude of potential transitions spanning the UV-visible-infrared spectrum. Despite recent advancements in MIR gain luminescence, the investigation of tunable MIR luminescence mechanisms remains a major technical challenge. Herein, an effective mechanism to modulate the local crystal field of rare earth ions by altering its crystal structure has been revealed, resulting in tunable broad-spectrum emission in the MIR luminescence range of 2800-3000 nm and multi-peak emission in the near-infrared band of Ho3+. Notably, the local crystal field of Ho3+ is adjusted by manipulating the lattice symmetry of CsPb1-xHoxBr3 perovskite through the incorporation of fluoride glass reticulation to control the crystal size of the perovskite and thereby modify the lattice symmetry of CsPb1-xHoxBr3 perovskite. The energy level transition of Ho3+ is influenced by adjusting the crystal field asymmetry, resulting in the splitting of the 5I6 energy level depending on the crystal field. This cleavage affects the transitions from the 5I5 level to 5I6 at 1480 nm and from 5I6 to 5I7 at 2880 nm. As 5I6 acts as the common upper level for the two emission peaks, the infrared peaks at 1480 nm and 2880 nm widen and develop into a dual-peak emission phenomenon. The infrared luminescence produced aligns closely with the distinctive infrared absorption peaks of carbon dioxide, leading to the development of a convenient, high-precision device for monitoring of CO2 concentration in hydrogen energy in real time. These findings are anticipated to pave the way for extensive utilization of novel tunable MIR luminescence.

3D Printed Ultra‐Fast Plastic Scintillators Based on Perovskite‐Photocurable Polymer Composite

AbstractAdditive manufacturing technology is exploited for the first time to build a complex geometry scintillator using a thermosetting photocurable resin filled by lead halide perovskite as an active material. To this aim, an innovative nanocomposite is developed based on Cs4PbBr6 perovskite powders as fillers and photocurable resin as matrix, adopting stereolithography as a manufacturing process. The use of high‐Z lead‐based perovskite filler is needed for the detection of ionizing radiation and the conversion into visible light, while the polymer matrix provides 3D printability. On the one hand, the inclusion of the perovskite‐based filler in the photocurable resin does not affect the rheological behavior and photocuring properties of the polymer matrix, making the composite suitable for 3D printing by stereolithography. On the other hand, the presence of the polymer does not affect the emission properties of the perovskite leading to the development of a fast response scintillator with significantly improved environmental stability. This work opens the avenue to the development of a completely new class of plastic scintillating materials.

Ultra-low dark current and high sensitivity lead-free perovskite–like photodetector realized by anti-solvent optimization Cs3Bi2I9 amorphous film

Compared with lead halide perovskite, bismuth-based perovskite has lower toxicity and air stability, demonstrating enormous potential for application, among them, Cs3Bi2I9 materials has been researched as an alternative to lead-based perovskite for application of optoelectronic devices. It is crucial for the realization of high-performance photodetectors which need high-quality perovskite thin films. Here, we prepared a lead-free, all-inorganic, Cs3Bi2I9 perovskite-like amorphous films by spin coating method, and diethyl ether was added as an anti-solvent at different times of spin-coating. The results show that the homogeneous and dense Cs3Bi2I9 amorphous films can be obtained by adding anti-solvent at 14seconds. Furthermore, Cs3Bi2I9 perovskite-like UV photodetector achieved extremely low dark current around ~pA range, high sensitivity of 1.10×104 was fabricated. Our research shows that the preparation of Cs3Bi2I9 amorphous films by the simple antisolvent-assisted spin-coating method are very promising for optoelectronic device.

Thermal characteristics of CsPbX3 (X =Cl/Br/I) halide perovskites

Halide perovskites represent a remarkably promising category of materials for the development of novel solar cells and opto-electronic devices. In this study, we used the neuroevolution machine learning potential to examine the thermal properties of CsPbX3 perovskites (X = Cl / Br / I). In alignment with previous research, our results disclose a pronounced correlation between lattice dynamics and thermal conductivity. Regardless of the specific perovskite variant, phonon band structure analysis revealed dynamical instability, characterized by overlapping phonon branches and densely packed optical branches beginning at imaginary low frequencies around 20i cm−1. We observed a significantly low lattice thermal conductivity of approximately 0.20W/(mK). This is due to the displacement of Cs atoms from their central positions and the deformation of the PbX6 octahedra, which results in lower phonon velocities and shorter phonon lifetimes.

Recent Advances in Metal Halide Perovskites for CO2 Photocatalytic Reduction: An Overview and Future Prospects.

The photocatalytic reduction of CO2 into valuable chemicals and fuels has become a significant research focus in recent years due to its environmental sustainability and energy efficiency. Metal halide perovskites (MHPs), renowned for their remarkable optoelectronic properties and tunable structures, are regarded as promising photocatalysts. Yet, their practical uses are constrained by inherent instability, severe electron-hole recombination, and a scarcity of active sites, prompting substantial research efforts to optimize MHP-based photocatalysts. This review summarizes the latest advancements in MHP-based photocatalysis. First the fundamental principles of photocatalysis are outlined and the structural and optical characteristics of MHPs are evaluated. Then key strategies for enhancing MHP photocatalysts, including morphology and surface modification, encapsulation, metal cation doping, heterojunction engineering, and molecular immobilization are highlighted. Finally, considering recent research progress and the needs for industrial application, challenges and future prospects are explored. This review aims to support researchers in the development of more efficient and stable MHP-based photocatalysts.

Probing the opto-electronic, thermoelectric, thermodynamic and elastic responses of lead-free double perovskite Li2ATlCl6 (A = Na and K) for potential photovoltaic and high- energy applications: A DFT study

The physical properties of double halide perovskite Li2ATlCl6 (A = Na and K) were examined through a first-principles study and semi-classical Boltzmann theory using the WEIN2k package, focusing on renewable energy generation and solar cell applications. Research on halides is growing within the optoelectronics and thermoelectric field and is anticipated to meet energy shortage demands. The volume-energy diagram confirms their structural stability, while the Pugh and Poisson ratios suggest ductility based on their elastic properties. The electronic properties were analyzed, and bandgaps were calculated using modified Becke-Johnson (mBJ) potentials, yielding bandgaps of 3.51 eV and 2.97 eV for Li2ATlCl6 (A = Na and K) respectively. The optical properties, evaluated using complex dielectric functions, indicated optimal light absorption in the infrared (IR) regions. Additionally, the thermoelectric (TE) properties of Li2ATlCl6 (A = Na and K) were analyzed using semi classical Boltzmann theory with a constant relaxation time approximation. At 1200 K, the calculated figures of merit (ZT) values were 0.75 and 0.69, respectively, indicating their potential for thermoelectric applications. Also, the thermodynamic properties are computed under pressure (0–15 GPa) and temperature (0–1200 K). These investigations offer a profound comprehension of these materials for their further employment. These results highlight their potential for optoelectronic device applications and are expected to encourage further experimental research on the feasibility of Li2ATlCl6 (A = Na and K) for optical devices.

Influence of Sn2+ doping to improve the charge transport and light-emitting properties of CsPbCl3 perovskites.

Doping B-site with metal ions is an emerging strategy to reduce lead toxicity and enhance the optoelectronic performance of lead halide perovskites. Also, the concentration of metal dopants plays an important role in achieving the desired electrical and optical properties of these halide perovskites. This work presents a simple chemical approach to synthesize pure and Sn2+ doped CsPbCl3 perovskites at room temperature. The dopant concentration was varied from 1 to 9 mol%. The structural, morphological, optical, thermal, and electrical properties of prepared perovskites are studied in order to check the optimal doping concentration along with to know the improvement in the optoelectronic properties required for LEDs and photovoltaic cells. It was observed that CsPbCl3 perovskites exhibit high photoluminescence intensity, blue/Violet emission, and high charge carrier mobility (up to 56.3 cm2/V-s) with a reduction in bandgap (up to 2.865 eV) after Sn2+ doping.

Water-soluble CsPbBr3@SiO2 nanocomposite: Enhancing stability in aqueous environments

CsPbBr3 all-inorganic lead halide perovskite nanocrystals have significant applications due to their unique photoluminescence properties. However, their poor stability and easy decomposition in water significantly limit their practical applications. Encapsulating cesium lead halide perovskite quantum dots (PQDs) within a stable shell has been proven to be an effective strategy for enhancing their stability. However, traditional methods of coating PQDs via direct hydrolysis of silicon source often result in particle aggregation or alterations in the original morphology and optical properties of the PQDs. In this study, we employed maleic anhydride to trigger the transformation of Cs4PbBr6 into CsPbBr3 nanocrystals (NCs). Simultaneously, maleic anhydride reacts with surface oleylamine (OAm) ligands to form maleic acid, which replaces the conventional oleic acid (OA) and oleylamine as ligands and surfactants. A uniform CsPbBr3@SiO2 nanocomposite was obtained, with a core size of approximately 9 nm and a shell thickness of about 15 nm. The absorption peak was located at 520 nm, with a full width at half maximum (FWHM) of around 25 nm. After one hour of dispersion in water, the water-soluble CsPbBr3@SiO2 nanocomposite maintained a high level of luminescence, with a photoluminescence (PL) loss of only 30.1 %. This approach enhances the affinity between PQDs and SiO2, improving the encapsulation efficiency of individual nanocrystals. This method not only prevents excessive hydrolysis and particle aggregation but also significantly enhances the water stability of CsPbBr3.

An emerging aspirant for solar cell and non-conventional energy applications: Lead free fluoro-perovskites A2TlInF6 (A = K, Rb)

In the present work; structural, electronic, optical, and thermoelectric properties of double perovskites A2TlInF6 (A = K, Rb) have been studied using the ab-initio method in conjunction with full potential Linear Augmented Plane Wave (FP-LAPW) method and PBE-GGA potential. Structural properties, cohesive energy, and formation enthalpy collectively confirmed the stability of the halide perovskites in a cubic structure with Fm3m symmetry. Electronic properties revealed the p-type semiconductor nature of both materials. The indirect band gap values for K2TlInF6 and Rb2TlInF6 were found to be 3.489 eV and 3.591 eV, respectively, with PBE. With PBE + SOC, the values dropped to 3.445 eV and 3.546 eV, respectively. Optical properties such as Dielectric function εω, Refractive Index nω, Extinction Coefficient κω, Optical Conductivity σ(ω), Reflectivity R(ω), Electron Energy Loss Function L(ω), and Absorption Coefficient αω were determined using PBE-GGA potential. BoltzTraP code was used to determine thermoelectric properties, namely, Seebeck Coefficient (S), Electrical Conductivity (σ), Thermal Conductivity (K), Power Factor (PF), and Figure of merit (ZT) which were studied in detail. The study suggests halide-based double perovskites may have the potential for solar energy utilization due to their high absorption coefficient, large values of refractive index, and optimal values of the figure of merit.

Halogen-independent optoelectronic properties in copper halides: A case study of K2CuX3 (X=Cl, Br)

The ternary copper halides have garnered significant attention as luminescent and nontoxic alternatives to lead halide perovskites for optoelectronic applications. These materials exhibit broadband emission, resulting in a visible light emission with an exceptionally high photoluminescence efficiency. In this study, taking the 1D K2CuX3 (X = Cl, Br) as typical examples, first-principles calculations were employed to elucidate the physical mechanisms underlying the efficient luminescent and halogen-independent optical properties. Our findings demonstrate (i) K2CuX3 has a direct band gap and a large transition matrix, which makes it more likely to undergo radiative recombination; (ii) the excellent defect tolerance opens up more possibilities for thermal relaxation and recombination; (iii) excitonic properties analysis revealed that the broadband emissions originate from self-trapped excitons, which is localized within a single [CuX4] tetrahedron. More important, due to the dominate contributions of Cu orbitals at the band edge in K2CuBr3 and K2CuCl3, the calculated STE emission energies (2.959 eV for K2CuBr3 and 2.953 eV for K2CuCl3) is strikingly similar. These defect tolerances and self-trapped excitons enable K2CuX3 to exhibit halogen-independent optoelectronic properties, which align with experimental observations. This study offers crucial insights into structural-emission relationships in copper halide materials.

Minimizing vacancy defects with Eu passivation strategy to enable highly efficient perovskite photovoltaics

The intrinsic ionic nature of metal halide perovskites facilitates the formation of abundant defects at grain boundaries (GBs) and surfaces, consequently diminishing the stability and photovoltaic performance of perovskite solar cells (PSCs). Due to the low formation energies and instability of Pb-I bonds, iodine (I) and lead (Pb) vacancies are prevalent high-density point defects. In this study, we explore the use of europium (Eu) as a novel passivator to concurrently address I and Pb vacancies through first-principles calculations. Our results demonstrate that Eu significantly lowers the defect formation energies and adjusts the bandgap, enlarged by vacancy defects, to align with the ideal Shockley-Queisser limit, indicating a strong potential for achieving high power conversion efficiency (PCE). Furthermore, Eu passivation markedly increases the activation energy barriers for ion migration, resulting in substantially reduced migration rates. This suggests a minimal likelihood of I and Pb ion migration on defected surfaces, underscoring Eu’s potential to mitigate hysteresis effects and enhance stability. This work advances our understanding of the passivation effects of rare earth elements and establishes a foundation for designing highly effective passivation strategies to achieve stable and efficient PSCs.